Science File

Lunar Rocks Show Birth of the Moon, Scientists Say

Most scientists agree that the moon is a celestial child of the Earth, having been blasted away from its parent by a giant impact with a Mars-sized object during the solar system's infancy.

Now a team of European researchers says it has discovered the moon's age, hidden in rock and soil samples retrieved by Apollo astronauts in the 1970s.

The researcher examined tungsten isotopes in the rocks and concluded that the collision occurred about 30 million to 50 million years after the formation of the solar system.

That's just a blip compared with the 4.5 billion years that the Earth and solar system have existed. That means the moon is almost as old as its parent.

Heat from the impact of the large body melted much of what would become the moon, forming a gigantic magma ocean that cooled into a dense, inorganic planetoid, the researchers wrote in an article published online Thursday by the journal Science.

The scientists from Germany, Switzerland and Britain were able to determine the moon's age by measuring the amount of tungsten-182 in metals contained in the lunar materials.

The dating process relied on the decay of hafnium-182 into tungsten-182 -- a process with a half-life of about 9 million years.

Previous studies have concluded that the moon was formed as many as 100 million years after the birth of the solar system. The authors of the new study say their method gives a more reliable estimate of the amount of tungsten-182.